Hi Platonides, thank you for your comment; indeed I haven't been clear enough. Your wording is much more closer to the spirit that was behind the decision, so I'll repeat it again:
* We /do/ accept content released under another free licences acceptable on Commons, and will not be "disqualifing" or in any other way removing from the contest any pictures that were released under another licence (and possibly uploaded through another tools), but * For the sake of simplicity & to make things easier for newcomers, we are only offering CC-BY-SA as the deafult licence for the UploadCampaigns.
And as for the other CC licences, we (myself and Basvb) have disabled them when starting the campaigns, but looks like people mistakenly turned them on again.
Again, Platonides, thanks for the corrections; it's appreciated!
Tomasz